1. Field of the Invention
The present invention relates generally to an optical module used to perform electro/optical conversion (E/O conversion) and/or opto/electrical conversion (O/E conversion) in electronic equipment such as a transmission device, and more particularly to a receptacle optical module having a receptacle mechanism for detachably holding an optical connector.
2. Description of the Related Art
An optical module to which an interface using an optical fiber is applied undergoes a manufacturing limitation on heat resistance of a coating of the optical fiber in mounting the module on a mother board (substrate) by soldering. That is, a pigtail type of optical module fixedly having an optical fiber cannot be originally adapted to a flow soldering process suitable for automation. In view of such a circumstance, there is provided a receptacle optical module having a receptacle mechanism for detachably holding an optical connector.
FIG. 1 is a perspective view of electronic equipment to which the present invention is applicable. In FIG. 1, a telephone exchange 2 is shown as the electronic equipment. The exchange 2 is provided with a rack 4 and a plurality of plug-in units 6 mounted in the rack 4 in a plug-in manner. Each plug-in unit 6 has a mother board (substrate) 8, a receptacle optical module 10 mounted on the mother board 8, and a connector 12 for electrically connecting the mother board 8 to another unit or device.
The details of the receptacle optical module 10 to which the present invention is applicable will be described later. The prior art of a receptacle optical module will now be described.
FIGS. 2 and 3 are a partially cutaway, plan view and a sectional view of a receptacle optical module in the prior art, respectively. This module has a housing 14 consisting of a lower housing 14A and an upper housing 14B. There are provided in the housing 14 two optical semiconductor assemblies 16 and a printed wiring board 18 to which each assembly 16 is electrically connected. To optically connect each optical semiconductor assembly 16 to an optical connector 19, a receptacle mechanism 20 for detachably holding the optical connector 19 is provided.
Each optical semiconductor assembly 16 has an optical semiconductor chip 22, leads 24 for electrically connecting the chip 22 to the printed wiring board 18, an optical fiber 26 optically coupled to the chip 22 by a lens (not shown), and a ferrule 28 in which the optical fiber 26 is inserted and fixed. The chip 22 is a light emitting element such as an LD (laser diode) and an LED (light emitting diode) or a photodetector such as a PD (photodiode). The receptacle mechanism 20 includes an elastically deformable sleeve (slitted sleeve) 32 for holding the ferrule 28 of the optical semiconductor assembly 16 and a ferrule 30 of the optical connector 19 in alignment with each other.
The printed wiring board 18 is provided with a plurality of lead pins 34 extending perpendicularly to the printed wiring board 18. The lead pins 34 are fixed by soldering to the mother board 8 through the lower housing 14A. Accordingly, both electrical connection of the printed wiring board 18 to the mother board 8 and mechanism fixing of the receptacle optical module to the mother board 8 are effected.
As shown in FIG. 3, attachment/detachment of the optical connector 19 with respect to the module is performed in a direction shown by an arrow substantially parallel to the mother board 8. Accordingly, in performing the attachment/detachment operation of the optical connector 19, a stress is generated in each lead pin 34 in such a direction as to bend each lead pin 34. As a result, the reliability of electrical connection between each lead pin 34 and the mother board 8 and between each lead pin 34 and the printed wiring board 18 is reduced.
As well understood with reference to FIG. 1, the attachment/detachment of each optical connector 19 must be carried out by moving the optical connector 19 in parallel to the mother board 8 at a position near the mother board 8. Accordingly, the attachment/detachment of each optical connector 19 is troublesome.
Further, it is necessary to ensure a space for the attachment/detachment of each optical connector 19 on the mother board 8. Accordingly, a degree of freedom of location of the receptacle optical module on the mother board 8 is small.